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PubMed1999

Fetal ultrasound biometry: 2. Abdomen and femur length reference values.

OBJECTIVE: To create reliable reference ranges and calculate Z scores for fetal abdomen and femur ultrasound biometry using a large sample size which is evenly distributed from 12 to 42 weeks of pregnancy. DESIGN: A prospective, cross-sectional study. SETTING: Obstetric clinics (outpatient and delivery units) at the University Hospital of Zurich. SAMPLE: The study data were obtained from 6557 pregnant women. METHODS: Only the first ultrasound examination between 12 and 42 weeks of each fetus with certainly established gestational age was used for analysis. No exclusions were made on the grounds of small-for-date birthweight, prematurity or other events several weeks after the examination. Separate regression models were fitted to estimate the mean and standard deviation at each gestational age for each parameter. RESULTS: A total of 5807 mean abdominal diameters and abdominal circumferences were derived from fetal transverse and anterio-posterior fetal abdominal diameter measurements. Fetal femur length was measured in 5860 instances. The charts, tables and regression formulae of the biometrical measurements are presented. A comparison of our charts with others showed no significant difference. Only Merz's centiles for abdominal biometry were lower and for femur length higher than ours. An application to calculate Z scores was developed using Excel (Microsoft Corporation, USA); the macros are presented in detail in the Figure 6 footnote. CONCLUSIONS: We have presented centile charts, tables and formulae for fetal abdominal diameter and circumference and femur length derived from a large and minimally selected sample size in a carefully designed cross-sectional study. Complete tables and regression formulae to calculate reference ranges and Z scores are presented to use in computer-aided evaluation of fetal ultrasound biometry.

Abdomen↗
PubMed2006

[Nasal bone biometry in the second trimester of gestation].

OBJECTIVES: To determine physiological variability range of the analyzed biometrical parameters and to establish optimal circumstances for fetal nasal ultrasound biometry. To evaluate preliminarily the value of fetal nasal biometry in the screening for aneuploidy. DESIGN: Ultrasound measurement of nasal bones length and nasal width in healthy fetuses and in fetuses with common aneuploidies. MATERIALS AND METHODS: Measurements of the analyzed parameters were undertaken in 681 euploid fetuses and 9 fetuses with common aneuploidies. Nasal bones length was measured with accordance to the same set of rules as determined by Cicero et al. in their publication relating to the first trimester nasal bones assessment. Nasal width was measured in the coronal plane between the alae. RESULTS: Relationship between the examined parameters and gestational age was described. The normal variability range of the analyzed parameters was determined and percentile charts created. In three out of five examined fetuses with trisomy 21 the nasal bones length was below the 5th percentile. In one out of five trisomy 21 fetuses the nasal width was over the 95th percentile. Regrettably the paucity of data obtained from affected fetuses does not allow drawing statistically founded conclusions. CONCLUSIONS: Fetal nasal biometry seems to be a valuable screening marker of trisomy 21 in the second trimester, requiring further studies.

Anthropometry↗
PubMed1995

Nurse or doctor: biometry for intraocular lens power calculation, who should measure?

Biometry for intraocular lens power calculation is critical to the refractive success of cataract surgery with intraocular lens implantation. The majority of ophthalmology departments in Scotland currently entrust this procedure to junior medical staff. In an attempt to streamline preoperative assessment of cataract patients we have changed our practice so that nurses now carry out biometry. This prospective study, in which the results of 336 eyes undergoing cataract surgery and intraocular lens implantation were examined, shows that appropriately trained nursing staff in our department are able to perform the measurements for biometry at least as accurately as junior medical staff.

Bias↗
PubMed2007

First-trimester fetal limb biometry in Chinese population.

OBJECTIVES: To establish reference ranges for fetal limb biometry obtained by transabdominal ultrasound examination at 12-14 weeks of gestation in Chinese women. METHODS: A total of 1489 normal singleton fetuses between 12(+0) and 14(+6) weeks of gestation were examined transabdominally by two experienced observers. The gestation was ascertained by measurement of fetal crown-rump length (CRL) or biparietal diameter (BPD) and head circumference (HC). The lengths of the humerus and femur were prospectively worked out. RESULTS: Gestation-specific reference ranges for limb measurements were calculated. The femur length (FL) (mean +/- SD) was 9.15 +/- 1.44 mm at 12-12(+6) weeks, 11.45 +/- 1.35 mm at 13-13(+6) weeks, and 13.64 +/- 1.60 mm at 14-14(+6) weeks; the corresponding humerus length (HL) (mean +/- SD) was 9.63 +/- 1.44 mm, 12.01 +/- 1.41 mm, 14.29 +/- 1.48 mm, respectively. CONCLUSIONS: There was a general increase in fetal limb biometry with gestation. Fetal limb length can be an early marker of early growth restriction as well as fetal skeletal dysplasia among women in the local population.

Adult↗
PubMed2004

Intraobserver and interobserver reproducibility of fetal biometry.

OBJECTIVE: To assess the intra- and interobserver reproducibility of ultrasound measurements of fetal biometric parameters. METHODS: We assessed the intraobserver and the interobserver agreement in measurements of fetal biparietal diameter (BPD), abdominal circumference (AC), head circumference (HC) and femur length (FL) on 122 singleton pregnancies. Patients were each examined twice by the first sonographer to determine the intraobserver reliability of measurements of fetal biometry. Subsequently, during the same ultrasound examination, a second blinded sonographer measured fetal biometric parameters to assess interobserver reliability. The consensus between and among observers was analyzed using the intraclass correlation coefficient (intra-CC) and interclass correlation coefficient (inter-CC) and the reliability coefficients (RC, alpha) for the four biometric measurements. A value > 0.75 was considered a reliable consensus for the intra-CC and inter-CC. A Bland and Altman plot was also created for the fetal biometric parameters to assess the repeatability of the measurements. RESULTS: Reliable consensus was observed for both the intra-CC and inter-CC and RC for all four biometric parameters. The intra-CC with the 95% CI and RC for the BPD, AC, HC and FL were as follows: 0.996 (0.995, 0.997), alpha 0.998; 0.994 (0.992, 0.996), alpha 0.997; 0.996 (0.994, 0.997), alpha 0.998; and 0.994 (0.992, 0.996), alpha 0.997, respectively. Similarly, the inter-CC with the 95% CI and RC for the same parameters were as follows: 0.995 (0.993, 0.997), alpha 0.998; 0.980 (0.971, 0.990), alpha 0.990; 0.994 (0.992, 0.996), alpha 0.997; and 0.990 (0.985,0.993), alpha 0.995, respectively. The Bland and Altman plots demonstrated a high degree of repeatability of BPD, AC, HC, and FL measurements. CONCLUSION: Our results demonstrate that the intra- and interobserver reproducibility of ultrasound measurements of fetal biometry are highly reliable.

Abdomen↗
PubMed2006

Feasibility and reproducibility of an image-scoring method for quality control of fetal biometry in the second trimester.

OBJECTIVES: The need for training programs and certification processes in fetal ultrasound has become obvious. The purpose of this study was to evaluate the feasibility of a score-based quality control system for fetal biometry in the second trimester. METHODS: Standard measurements of biparietal diameter and head circumference, abdominal circumference, and femur length at 20-24 weeks had been made by four operators using the same ultrasound machine. Twenty-five of each of the cephalic, abdominal and femoral images with the calipers in place were selected arbitrarily from each operator's ultrasound database and anonymized. These 300 images were analyzed by three experienced reviewers blinded to the operator's identity. Each image was first evaluated subjectively and then scored according to six criteria for abdominal and cephalic measurements and four criteria for femur length making a six-point score for abdominal and cephalic biometry and a four-point score for femur length. For subjective evaluation, inter-reviewer differences were analyzed using percentage agreement and adjusted kappa. For objective evaluation, a difference in scoring of one point or less among reviewers was considered good agreement. Intrareviewer variability was assessed using 40 images of each type of examination selected arbitrarily. RESULTS: The distribution of scores was similar between reviewers. One operator obtained significantly lower scores whereas the other three had good and comparable results. There was no statistical difference in the mean score attributed by each reviewer and agreement was good in 84-90% of the cases. Intrareviewer agreement was good in 90-100% of the cases, with similar scores for each reviewer. CONCLUSION: A quality control policy based on image scoring is feasible and allows for fair to good inter- and intrareviewer reproducibility. The potential contribution of this approach to assess the quality of routine ultrasound examinations should be tested on a larger scale.

Abdomen↗
PubMed2006

French fetal biometry: reference equations and comparison with other charts.

OBJECTIVES: To construct new reference charts and equations for fetal biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC) and femur length (FL), using a large sample of fetuses examined at 15-40 weeks in France, and to compare them with previous references. METHODS: The study data were obtained over a continuous 1-year period from a population of pregnant women undergoing ultrasound examination. Excluded were those with a known abnormal karyotype or congenital malformation, multiple pregnancies, and those with no first-trimester dating based on crown-rump length. No fetuses were excluded on the basis of abnormal biometry or birth weight. For each measurement, separate regression models were fitted to estimate both the mean and the SD at each gestational age. RESULTS: Full biometric measurements were obtained for 19 647 fetuses. New charts and reference equations are reported for BPD, HC, AC and FL. Prediction intervals for the new reference charts were similar to those of previous ones, whereas there were some differences in predicted centiles. CONCLUSION: We present new French reference charts and equations for fetal biometry. They can be used easily to compute centiles and Z-scores to control the quality of biometric assessments and to evaluate their performance relative to other references.

Abdomen↗
PubMed2006

Biometry of the pubovisceral muscle and levator hiatus in nulliparous Chinese women.

OBJECTIVES: To identify using three-dimensional (3D) ultrasound the morphological features and normal biometry of the levator hiatus in nulliparous Chinese women and to explore ethnic differences between these measurements and those in nulliparous Caucasian women. METHODS: 3D sonographic data from 59 nulliparous Chinese women (aged 19-38 years) who had no pelvic organ prolapse and no symptoms of pelvic floor dysfunction were retrieved from an image dataset and analyzed by offline post-processing. The pubovisceral muscle and levator hiatus were measured in the planes of maximal pubovisceral muscle thickness and minimum hiatal dimension, respectively. In addition, the genitohiatal and levator ani angles were measured. These values were compared with those in a published study of Caucasian women. RESULTS: In Chinese women there was no relationship between minimum anteroposterior (AP) hiatal diameter and minimum lateral hiatal diameter. Body weight was correlated with hiatal area and minimum AP hiatal diameter (r = 0.391, P = 0.003 and r = 0.378, P = 0.004, respectively), whereas body mass index was correlated only with minimum AP hiatal diameter (r = 0.349, P = 0.008). There was a significant difference in average pubovisceral muscle thickness (P = 0.001) between nulliparous Chinese and Caucasian women. CONCLUSIONS: Body weight, body mass index, and ethnicity are factors affecting the biometry of the levator hiatus in Chinese nulliparous women.

Adult↗
PubMed2005

Fetal cerebral biometry: normal parenchymal findings and ventricular size.

Assessing fetal cerebral biometry is one means of ascertaining that the development of the fetal central nervous system is normal. Norms have been established on large cohorts of fetuses by sonographic and neurofetopathological studies. Biometric standards have been established in MR in much smaller cohorts. The purpose of this paper is to analyse methods of measuring a few parameters in MR [biparietal diameter (BPD), fronto-occipital diameter (FOD), length of the corpus callosum (LCC), atrial diameter, transverse cerebellar diameter, height, anteroposterior diameter and surface of the vermis] and to compare US and MR in the assessment of fetal cerebral biometry.

Biometry↗
PubMed2003

Fetal MRI: normal gestational landmarks for cerebral biometry, gyration and myelination.

PURPOSE: Up until the last 10 years, normal cerebral gestational landmarks were assessed by ultrasonographic and fetopathologic studies. The purpose of this paper is to display the possibilities provided by fetal MRI in the evaluation of fetal cerebral biometry, normal sulcation and myelination. METHODS: Two hundred and twenty-five fetuses (with a normal brain) were studied prospectively using a standardised method. The gestational age ranged from 22 to 38 weeks. The main data concerning biometry of various cerebral structures at those terms are given. DISCUSSION: In contrast to ultrasound, MRI allows measurements of brain (and not skull), which are available independently of the position of the fetal head. The timing of the appearance of the different sulci is also available using MRI. It is considered to be a good marker of fetal brain maturation. The biochemical modifications contemporary to myelination make it possible to evaluate this phenomenon in the fetal brain using MRI.

Aging↗
PubMed2004

Ultrasound biometry of Arabian fetuses.

OBJECTIVE: To establish fetal ultrasound biometry charts for Arabian fetuses between 14 and 40 weeks of gestation. METHOD: Cross-sectional fetal ultrasound data of normal singleton pregnancies, which had been performed over a period of 7 years, were retrieved. Only pregnant Arab women with certain last menstrual period dates and/or early ultrasound examinations were included. Each fetus contributed to only one set of data. Normal ranges for biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), and femur length (FL) were established. The mean and 5th and 95th percentiles at 18th, 28th, and 36 weeks of gestation were compared with similar ranges of published data from pregnancies of American and Anglo-Saxon population. RESULTS: Fetal ultrasound biometry has been established for our local population. Comparing our data with Western population emphasizes the presence of significant variation in fetal morphometric measurements, particularly in the later weeks of gestation and at the extremes of the range of fetal size. CONCLUSION: The clinical significance of this variation differs according to the primary objective of ultrasound fetal measurements. For estimation of fetal age, usually by head and femur measurements in early gestation, ethnic variation seems to have limited significance. Whereas for estimation of fetal growth and/or weight in the third trimester, based on abdominal circumference, the use of given points, e.g., 10th or 5th percentile derived from other population charts, has the potential of either over- or underdiagnosis of IUGR fetuses. The adoption of locally developed charts is recommended.

Anthropometry↗
PubMed2006

Influence of severity of nuclear cataract on optical biometry.

PURPOSE: To compare preoperative and postoperative measurements of the axial length (AL) performed with the IOLMaster (Carl Zeiss Meditec) to evaluate the effect of nuclear cataract on the optical biometry. SETTING: Department of Ophthalmology, Medical University of Vienna, Vienna, Austria. METHODS: In 245 consecutive eyes of 162 patients scheduled for cataract surgery, type and severity of cataract was evaluated using the Lens Opacities Classification System III. Preoperative and postoperative axial length measurements were performed with the IOLMaster. The postoperative readings of AL were corrected for the IOL optic material implanted. RESULTS: The preoperative AL measurements were 0.07 mm +/- 0.05 (SD) (range -0.18 to 0.11 mm) longer than the postoperative measurements (P<.001). These differences in AL were only weakly correlated (r = -0.28, P = .01) with the nuclear cataract grade, mean 3.5 +/- 0.9. CONCLUSION: In this study, AL measurements with optical biometry using the IOLMaster were not influenced by the severity of nuclear cataract to a clinically relevant degree. Furthermore, it was found that AL in the phakic eye was overestimated by about 0.07 mm because of a slightly too low value of the group refractive index used for the crystalline lens.

Adult↗
PubMed1996

Estimating the date of confinement: ultrasonographic biometry versus certain menstrual dates.

OBJECTIVE: Our purpose was to evaluate the clinical implications of current pregnancy dating policies in a population where routine ultrasonography is performed in the first half of pregnancy. STUDY DESIGN: A total of 34,249 computer files of singleton pregnancies that had both "certain" menstrual dates and ultrasonographic biometry were retrieved from the East Midlands Obstetric Database. The estimated dates of delivery were calculated by five different methods: menstrual dates alone, ultrasonography alone, or a combination of both with menstrual dates used if the discrepancy with the ultrasonography dates was within 7, 10, or 14 days, respectively. The accuracy of each method in predicting the actual date of delivery was calculated. Differences among methods were evaluated with nonparametric tests. RESULTS: Compared with use of certain menstrual dates, ultrasonographic dating led to a 70% reduction in the number of pregnancies considered postterm. Delivery occurred within +/- 7 days of the estimated date of confinement in 49.5% cases when menstrual dates alone were used and in 55.2% if ultrasonography alone was used; for +/- 10 days, the corresponding figures were 64.1% and 70.3%. Scan dating alone was significantly better in predicting the actual date of delivery than any of the dating policies taking menstrual dates alone or in combination with ultrasonography. CONCLUSIONS: Even if menstrual dates are considered "certain," there is no advantage in taking them into consideration for calculating the expected date of delivery if a dating ultrasonography result is available. Dating by ultrasonographic biometry in the first half of pregnancy results in a more accurate prediction of the delivery date than using menstrual data alone or in combination with ultrasonography.

Biometry↗
PubMed1998

New Down syndrome screening algorithm: ultrasonographic biometry and multiple serum markers combined with maternal age.

OBJECTIVE: We compared the Down syndrome screening efficiency of a new algorithm that combines humerus length measurement and serum analytes versus that of the traditional triple-analyte serum screen. STUDY DESIGN: Humerus length measurements were obtained prospectively in 1743 midtrimester (14 to 24 weeks) singleton fetuses before genetic amniocentesis. All patients had triple-marker serum screening before amniocentesis. Data on humerus length were expressed as multiples of the median, and were normalized by log transformation. Backward multiple stepwise logistic regression analysis was performed to determine which combination of biometry and serum markers best predicted fetal Down syndrome. The screening efficiency of the traditional triple-analyte algorithm was compared with that of a new multivariate gaussian algorithm that combined biometry and serum markers. RESULTS: There were 31 (1.8%) fetuses with Down syndrome in the study population. In the regression analysis humerus length, human chorionic gonadotropin, alpha-fetoprotein, and maternal age were significant predictors of Down syndrome, but unconjugated estriol was not. The combined algorithm (humerus length, human chorionic gonadotropin, and alpha-fetoprotein and age) was superior to the traditional triple screen for Down syndrome detection. The sensitivities at fixed false-positive rates were consistently higher in the combination than in the triple-screen protocol. For example, at a 10% false-positive rate the sensitivities were 65.0% and 52.3%, respectively. Similarly, at a 15% false-positive rate the sensitivities were 73.5% and 55.0%, respectively. CONCLUSION: A new screening algorithm combining humerus length and serum analytes was superior to the traditional triple screen. Although we used a high-risk population in this study, it is expected that the observed superiority of the combination screen would persist in a population of younger women. The development of a combined biometric and serum analyte screening algorithm for estimating individual odds could represent an advance in prenatal Down syndrome screening.

Algorithms↗
PubMed2004

[Comparison between optical and acoustical biometry].

INTRODUCTION: Our current standard biometric measurement was compared to IOL-Master measurement. MATERIALS AND METHODS: One hundred sixty-two consecutive cataractous eyes were examined using the IOL-Master as well as the acoustic biometry combined with the Javal-Keratometer. In all eyes, the intraocular lens power to be implanted was chosen by means of the SRK/T formula, based on the measurements conducted with our standard method. The postoperative refraction achieved, obtained at least 6 weeks after surgery from the treating ophthalmologists, was communicated to us. The results were compared and analysed statistically. RESULTS: Comparison of the eye lengths, as well as of the keratometric measurements showed good correlation between the measurements obtained by both methods, the acoustic biometry yielding significantly (p < 0.001) shorter axial-lengths than the IOL-Master (r = 0.985) and the Javal yielding significantly (p < 0.001) higher mean corneal refraction power than the IOL-Master. The accuracy of the refraction obtained postoperatively compared to the preoperative aim was better with our standard method compared to the IOL-Master. CONCLUSIONS: The presumed systemic differences in measurement results could be verified. The IOL-Master currently has two advantages: it provides a substantial gain in time and the measurements can be delegated. Analysis of the subgroups showed that the "A" constant should be adapted with the IOL-Master to improve predictability of the postoperative refraction.

Adult↗
PubMed2005

[Optical biometry of eyes corrected by phakic intraocular lenses].

PURPOSE: The aim of this study was to determine whether eye length measurements obtained with the IOL Master (Zeiss Humphrey) before and after phakic IOL implantation would show any changes. METHODS: In a prospective study, we used the IOL Master to measure optical biometry in 25 myopic eyes of 15 patients before and after phakic IOL implantation (PRL, ICL, Artisan). The differences between both axial length measurements were calculated and compared using a nonparametric Wilcoxon test. RESULTS: The difference between the preoperative and postoperative measurements ranged from -0.16 mm to 0.06 mm and averaged -0.016 mm, which was not statistically significant (p=0.20). Both measurements correlated in a highly positive manner (r=0.999; p<0.0001). The reproducibility of the preoperative and postoperative axial length measurements was very high (coefficient of variation=0.09% and 0.07%, respectively). The precision was 26 microm for preoperative measurements and 19 microm for postoperative measurements. CONCLUSION: Our results showed that postoperative measurements of axial length are highly comparable to preoperative measurements and that optical biometry can achieve highly precise and reliable axial length measurements in eyes with phakic IOLs. This application becomes clinically relevant in evaluating eyes with phakic IOLs that might require cataract surgery. Hence, accurate axial length measurements in eyes with phakic IOLs will be extremely important when cataract occurs in these eyes and when the preoperative measurements are no longer available.

Adult↗
PubMed2001

Reproducibility of optical biometry using partial coherence interferometry : intraobserver and interobserver reliability.

PURPOSE: To evaluate the intraobserver and interobserver variability in axial length (AL), anterior chamber depth (ACD), and corneal radius measurements using an optical biometry instrument based on partial coherence interferometry (PCI). SETTING: Johannes Gutenberg University, Mainz, Germany. METHODS: In this observational case series and interobserver reliability trial, 30 healthy, emmetropic to moderately myopic eyes of 15 volunteers were evaluated. The AL, ACD, and corneal radius were measured 20 times in 10 eyes by 1 observer to evaluate the intraobserver variability. To evaluate the interobserver variability, the measurements were taken in 20 eyes by 5 different observers. Measurements were performed using the IOLMaster (Carl Zeiss) based on PCI. The data description is based on coefficients of variation and the statistical inference on reliability estimation based on analysis of variance. The main outcome measures were intraobserver and interobserver variability and reliability in AL, ACD, and corneal radii. RESULTS: The intraobserver variability (SD) was +/-25.6 microm for AL, +/-33.4 microm for ACD, and +/-12.9 microm for corneal radius. The coefficients of variation were 0.1%, 0.9%, and 0.17%, respectively. The interobserver variability (SD) was +/-21.5 microm for AL, +/-29.8 microm for ACD, and +/-15.9 microm for corneal radius. The coefficients of variation were 0.09%, 0.82%, and 0.21%, respectively. The reliability was 99.9% for AL, 97.8% for ACD, and 99.8%/99.5% for corneal radius (r1/r2). The slightly reduced reliability in ACD measurement was caused by a reduced intraobserver reliability of 1 of the 5 observers (R = 0.87). CONCLUSION: Partial coherence biometry using the IOLMaster for AL measurement was highly reliable, offering observer-independent measurement results.

Adult↗
PubMed2003

Contact versus immersion biometry of axial length before cataract surgery.

PURPOSE: To compare the repeatability and agreement of contact and immersion ultrasound (US) biometry of axial length. SETTING: Prince of Wales Hospital, Sydney, Australia. METHODS: This prospective stratified randomized study comprised 36 patients with a preoperative refractive error less than 4.00 diopters (D) sphere or 2.00 D cylinder who were recruited before cataract surgery. Each of 3 operators measured both eyes of 12 patients by contact and immersion US techniques. A repeat measurement by both techniques was performed by the same operator in 6 cases and by a different operator in the other 6. Repeat and operator effects were examined. RESULTS: The mean and standard deviation of the measurement sets were compared, and the differences between repeat measures were calculated. Axial length measurement was longer with the contact method than with immersion by 0.03 mm (P =.04). The repeatability of the 2 techniques was similar. CONCLUSIONS: When the measurement set was repeated, the precision of contact US biometry was comparable to that of immersion, with no clinically significant difference in mean axial length measurements.

Adult↗